always overwrite collage after taking new image

app/models/picture_set.rb

@@ -38,7 +38,7 @@ def create(date: Time.now.getlocal.strftime(DATE_FORMAT))
       # wait until convert jobs are finished
       until jobs.none?(&:status) do end
       picture_set.create_animation
-      #background_thread { picture_set.combine_images } if OPTS.render_collage
+      background_thread { picture_set.combine_images(overwrite: true) } if OPTS.render_collage
       (1..4).each { |i| GpioPort.off(GpioPort::GPIO_PORTS["PICTURE#{i}"]) }
       GpioPort.off(GpioPort::GPIO_PORTS['PROCESSING'])
       picture_set

spec/models/picture_set_spec.rb

@@ -53,10 +53,10 @@
 
     before do
       expect(FileUtils).to receive(:mkdir).with(/fixtures\/filesystem\//)
+      expect(PictureSet).to receive(:new).and_call_original
     end
 
     it 'takes new picture' do
-      expect(PictureSet).to receive(:new).and_call_original
       expect(Syscall).to receive(:execute).with(/gphoto2 --capture-image-and-download/, anything).exactly(4).times
       expect(Syscall).to receive(:execute).with(/convert/, anything).exactly(5).times
       expect(File).to receive(:exist?).with(/_animation.gif/).and_return(false)
@@ -67,7 +67,6 @@
     end
 
     it 'raises if image capture failed' do
-      allow(PictureSet).to receive(:new).and_call_original
       allow(Syscall).to receive(:execute).with(/gphoto2 --capture-image-and-download/, anything)
       allow(GpioPort).to receive(:on)
       allow(GpioPort).to receive(:off)